Welcome!

Is this what you're looking for?

http://processing.org/reference/noLoop_.html

Note: your subject line should reflect the nature of the question, not your current newbie state... Would be nice to edit your first message to improve this line.

Insentience is right, millis() is what you look for: it is at 0 at the start of the sketch, and increases... each millisecond. So once it has reached the wanted value (test >= not ==), you can stop the sketch with exit().